1. Field of the Invention
This invention relates to a multi-circuit feedthrough capacitor assembly designed so that a plurality of circuits each containing a feedthrough capacitor can be handled as a single part.
2. Description of the Prior Art
Heretofore, various kinds of feedthrough capacitors have been proposed, including those which can be handled as chip parts, such as a feedthrough capacitor chip 1 shown in FIG. 11.
The feedthrough capacitor chip 1 has main body 2 constructed as a laminate, for example, of dielectric ceramic layers. The main body 2 comprises a portion in which ceramic layers 4 each having an inner electrode 3, as shown in FIG. 12, longitudinally extending thereacross and ceramic layers 6 each having an inner electrode 5, as shown in FIG. 13, transversely extending thereacross are alternately laminated.
The main body 2, as shown in FIG. 11, is formed with outer electrodes 7 at opposite ends thereof, and outer electrodes 8 at opposite lateral sides thereof. The outer electrodes 7 are electrically connected to the inner electrodes 3 at opposite end surfaces of the main body 2, while the outer electrodes 8 are electrically connected to the inner electrodes 5 at opposite lateral surfaces of the main body 2. These outer electrodes 7 and 8 extend to the lower surface of the main body 2, though not shown in FIG. 11.
It has been common practice to mount such feedthrough capacitor chips 1 one by one on a printed circuit board. Therefore, in a circuit which requires a number of feedthrough capacitors, a number of feedthrough capacitor chips 1 are required and hence time and labor involved in mounting and soldering them increase, leading to a rise in cost.
To eliminate the drawback described above, a multi-circuit feedthrough capacitor chip 11 shown in FIG. 14 has been proposed. This multi-circuit feedthrough capacitor chip 11 has also a main body 12 in the form of a laminate of dielectric ceramic layers. Present in the main body 12 are ceramic layers 17 each having a plurality of band-like inner electrodes 13 through 16 vertically extending thereacross, as shown in FIG. 15, and ceramic layers 19 each having a single inner electrode 18 horizontally extending thereacross, as shown in FIG. 16, said ceramic layers 17 and 19 being alternately laminated.
The outer surface of the main body 12 is formed with outer electrodes 20 through 24 respectively in pairs. The outer electrodes 20 are electrically connected to the inner electrodes 13, the outer electrodes 21 to the inner electrodes 14, the outer electrodes 22 to the inner electrodes 15, the outer electrodes 23 to the inner electrodes 16, and the outer electrodes 24 to the inner electrodes 18. The outer electrodes 20 through 24 extend to the lower surface of the main body 12, though not appearing in the figure.
Such multi-circuit feedthrough capacitor chip 11 can provide a circuit including four feedthrough capacitors each formed between one of the inner electrodes 13 through 16 and the inner electrode 18.
Therefore, such multi-circuit capacitor chip 11 is advantageous in that despite having a plurality of feedthrough capacitors, it can be used as a single part.
However, the conventional feedthrough capacitor chip 11 has a disadvantage that the nearer to the middle of the main body 12 is the circuit positioned, the more the inductance that is produced in the inner electrode 18 connected to the earth line and the less the insertion loss that is produced. For the same reason, there has been a problem that crosstalk is produced in relatively large amounts.
Further, since the multi-circuit feedthrough capacitor chip 11 has its main body 12 exposed, it is liable to be influenced by environmental conditions including humidity; thus, there has been a drawback that it is lacking in reliability.
Further, each time the number of circuits requiring feedthrough capacitors or circuit conditions are changed, it is necessary to prepare a feedthrough capacitor chip of different design. This is extremely disadvantageous from the standpoint of production cost particularly where demands are varied.